Yeah mate...where the pipes are (metal tread area).
I may have just assumed you were putting tanks here...not sure if you said you were or not..?I was just wondering what you personaly thought you would need (gap between bottom/top tanks) for bottom tank access.
I've got plans for building racks and I'm trying to work out the minimum gap needed..whilst not leaving it to tight (would like to get my hand in and around bottom tank with quite a bit ease). Every inch counts here (for me), as height-wise it's very tight...for the planned 2 tier rack.
Kev